1. Field of the Invention
The present invention relates to a system and method for data security. More particularly, the present invention relates to a cryptographic device which preserves the integrity of audio by preventing the audio from being unknowingly altered.
2. Description of Art Related to the Invention
As personal computers, networks and other electronic devices supporting digital data transfers have become more widely used, the importance of data security has increased dramatically. For data security to be highly reliable, it must preserve the "integrity" of data transmitted between two electronic devices by ensuring that the data is not altered during transmission. However, with advancements in electronic technology, it is becoming quite difficult to detect alterations of data.
In an effort to preserve data integrity, a technique called "time stamping" has recently been developed and is commercially offered from Surety Technologies, Inc. of Chatham, N.J. As shown in FIG. 1, the time-stamping technique involves a digital data set 110, such as a stream of video as shown, being processed (or "hashed") in accordance with a cryptographically secure hash algorithm 120 (e.g., "MD5" algorithm developed by RSA Data Security, Inc. of Redwood City, Calif.). This causes the digital data set 110 to be mapped from its arbitrary size into a significantly smaller, fixed size referred to as a "digest" 130. No information about the digital data set 110 may be derived from the digest 130.
Typically, the digest 130 is electronically transferred to a centralized system 150 (e.g., a mainframe computer or a collection of personal computers) as indicated by a data path 140. Subsequently, the digest 130 in combination with a number of other digests 160.sub.1 -160.sub.x ("x" being a positive whole number, x&gt;1) from different electronic devices are hashed to produce an intermediate digest 170.sub.1 -170.sub.y ("y" being a positive whole number, y&gt;1) as shown. The variety of intermediate digests 170.sub.1 -170.sub.y are hashed together until a composite digest 190 is generated from intermediate digests 180.sub.1 and 180.sub.2. Next, the composite digest 190 is widely published (e.g., printed in a publication, disseminated to its sources, stored in a database, etc.) to establish that the digital data set 110 was in existence at least before the publication of the composite digest 190.
While this time-stamping mechanism is useful in establishing that the digital data set 110 existed before the publication date, there is no current mechanism to "time-bracket" data, in this case video and its complementary audio, to indicate that both the audio and video were captured within the prescribed period of time ranging from a first time period to a second time period.